Irnich W
Pacing Clin Electrophysiol. 1980 May;3(3):292-301. doi: 10.1111/j.1540-8159.1980.tb05236.x.
Describing mathematically, the intensity duration curves of electrostimulation by hyperbolas, Lapicque introduced two terms which characterized the functional relationship: "Rheobase" was the lowest intensity with indefinite pulse duration which just stimulated muscles or nerves. "Chronaxie" was that pulse duration at which the threshold intensity was twice that of the rheobase. Up to now, both terms have never played an important role in cardiac pacing. However, it can be shown that the chronaxie, especially, is an important parameter--influenced by several factors such as electrode size, material, and stimulation mode--which may help match the generator to its electrode. Practical consequences may be derived from the concept of chronaxie: 1) A pulse duration longer than the chronaxie is not desirable because current consumption is increased without decreasing the threshold significantly. 2) Pacing with constant current needs twice that pulse duration of constant voltage stimulation. 3) Smaller electrodes are more favorable because the pulse duration they need may be reduced without losing safety. 4) Estimation of the safety margin with decreasing output of the generator or with programmable pulse duration is possible if the chronaxie of a specific electrode is known.
拉皮克用双曲线对电刺激的强度-持续时间曲线进行数学描述时，引入了两个表征功能关系的术语：“基强度”是指在脉冲持续时间无限长时刚好能刺激肌肉或神经的最低强度。“时值”是指阈值强度为基强度两倍时的脉冲持续时间。到目前为止，这两个术语在心脏起搏中从未发挥过重要作用。然而，可以证明，尤其是时值，是一个重要参数——受电极大小、材料和刺激模式等多种因素影响——这可能有助于使发生器与电极相匹配。从时值的概念可以得出一些实际结论：1）脉冲持续时间长于时值是不可取的，因为在不显著降低阈值的情况下会增加电流消耗。2）恒流起搏所需的脉冲持续时间是恒压刺激的两倍。3）较小的电极更有利，因为在不降低安全性的情况下可以缩短它们所需的脉冲持续时间。4）如果已知特定电极的时值，那么在发生器输出降低或脉冲持续时间可编程的情况下，就可以估计安全裕度。
